1. Technical Field
The present disclosure generally relates to electronic circuits and, more specifically, to the detection of local dynamic disturbances in an integrated circuit.
2. Description of the Related Art
Many techniques aiming at detecting the occurrence of a dynamic disturbance in an integrated circuit are known. Such disturbances, when they are intentional, are due to fault injection attempts for disturbing the operation of a circuit. Such is especially the case when the circuit performs cryptographic operations manipulating so-called secret quantities. The introduction of a local disturbance (for example, by laser attack) causes one or several changes in logic circuits that may be exploited to discover the secret quantities.
A first category of detectors is exploited in phases of testing of an integrated circuit to assess its resistance to such attacks. Dedicated circuits, which are submitted to disturbances to assess the dynamic behavior of the circuit, are then provided.
A second category of detectors relates to detectors exploited during the lifetime of the product. The result of the detection is then exploited by the circuit to take possible counter-measures against the detected disturbance.
Detectors that exploit a disturbance of a clock signal are particularly capable of detecting dynamic disturbances. Such detectors often exploit two clock signals generated by identical circuits and placed at different circuit locations. The generated clock signals are then compared, to detect the occurrence of a possible disturbance on one of the two signals. A difficulty is that, despite all the care that may be taken to have identical clock generation circuits, in practice, a drift is typically present and it is accordingly difficult to tell a short dynamic disturbance from a phase shift due to manufacturing.